Water Tank Holds 32 gallons should be 48?

[ToddT]

Went dry camping a few weeks ago and was frustrated that after one day our water tank level was showing 1/3 and after two days was showing empty. Today I ran a test and filled the tank and measured as it drained. At full the meter said full. After dropping 5 gallons, the meter said 2/3. After dropping between 10 and 15 gallons the meter went to 1/3. After 25 gallons the meter said empty. I dropped a total of only 32 gallons. Even if the HWH is ten gallons (which I doubt) I am still cheated out of six or more gallons.

I have read other posts on tanks being smaller than listed/advertised.Is this typical? We dry camp often and I was counting on having a full load of water for the weekend.

[Murff]

Does the advertised tank capacity include the hot water tank?

Murff

[Old skipper]

Try filling the tank until water comes out the over flow then open the low point drain and measure how much water is drained. The fresh water tank on the Seneca is close to as advertised so I would expect most tanks to be close.

[ToddT]

Originally Posted by Old skipper

Try filling the tank until water comes out the over flow then open the low point drain and measure how much water is drained. The fresh water tank on the Seneca is close to as advertised so I would expect most tanks to be close.

I will have to mess with it more later. I noticed that the unit is not as level as it could be, and is in fact sloped slightly away from the tank drain. So the missing capacity could simply still be in the tank. I am taking it out this weekend and will level it better when I get back. Then I will try again and drain the hot water heater too.

[oldmanAZ]

For your boondocking weekends, I'm sure you already know....

The OEM tank gauges are often not very accurate.
Siphoning of fresh water through the vent hoses happens frequently when traveling.

[MnBob]

Not sure what is meant when oldmanAZ writes "Siphoning of fresh water through the vent hoses happens frequently when traveling" Can you explain more? Thanks.

[oldmanAZ]

Originally Posted by MnBob

Not sure what is meant when oldmanAZ writes "Siphoning of fresh water through the vent hoses happens frequently when traveling" Can you explain more? Thanks.

Sure.
Many (most?) of us that travel with full fresh water tanks have arrived at our destination with less water than we started out with. The problem was that the motion while traveling fills the water tank vent line and as that water runs out it creates a siphon that pulls water out of the tank.

There are numerous posts on this site about ways to stop this from occurring; plugs in the vent line, valves in the vent line, or rerouting the vent line to prevent the siphoning. When adding water to the tank air needs to escape through the vent lines, so plugs need to be removed or valves need to be opened.

That's it in a nutshell.